Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$241.42	10.373%	$266.4625	$266.46	$266.45	$266.50
Purchase #2	$62.92	4.111%	$65.5066	$65.51	$65.50	$65.50
Purchase #3	$29.65	13.326%	$33.6012	$33.60	$33.60	$33.60
Purchase #4	$50.93	5.851%	$53.9099	$53.91	$53.90	$53.90
Purchase #5	$137.81	12.367%	$154.853	$154.85	$154.85	$154.90
Purchase #6	$33.49	13.120%	$37.8839	$37.88	$37.90	$37.90
Purchase #7	$115.55	5.676%	$122.1086	$122.11	$122.10	$122.10
7 purchase totals =	$671.77		$734.3257	$734.32	$734.30	$734.40